1993 Isuzu Amigo battery cabels smoking

I went out to start my car and it tryed to start and then died and the oil pressure gage went crazy and then smoke came out from under the hood, i opened the hood and both of the battery cabels were burnt and melted. I replaced the cabels and the battery. I went to go hook up the cabels and i put the neg. on and then touched the pos. to the battery and the car tryed to start with out the key in it. So i went and had the starter checked it passed and problem is still there, so i replaced the ignition swicth and problem still there, i checked for shorts and ground they look good. I also disconnected the starter and hooked up the battery and no sparks on the battery post. I need help.